Weather Data Calculations; Temperature; High And Low Temperature; Barometric Pressure - DAVIS WeatherLink Software User's Manual

W D
E A T H E R A T A
The following section details how the software calculates the data for each
weather function to arrive at an entry for the archive memory or database.

Temperature

The Weatherlink samples the temperature reading from the station a number of
times during the interval and then averages all those readings to arrive at the
average temperature for the interval. The number of times the Weatherlink sam-
ples the temperature depends on the archive interval.
A
RCHIVE
1 minute
5 minutes
10 minutes
15 minutes
30 minutes
1 hour
2 hours

High and Low Temperature

The first time the Weatherlink samples outside temperature during the interval it
writes that value into both a high and low register in memory. Every subsequent
time the Weatherlink samples the temperature, it compares the current value to
the value in the registers and if the current value is higher or lower, replaces the
old value with the current value. Whatever value is in the register at the time of
the archive gets written into archive memory.

Barometric Pressure

The Weatherlink samples the barometric pressure at the time of the archive and
writes that value into the archive memory.

Wind Speed

The Weatherlink samples the wind speed reading the same number of times per
interval as temperature and averages the readings together to arrive at the aver-
age wind speed for the interval.

High Wind Speed

The Weatherlink is constantly checking for a new high wind speed. The highest
wind speed value recorded during the interval gets written into archive memory.

Wind Direction

The Weatherlink samples the wind direction reading the same number of times
per interval as temperature. If wind speed is greater than 0 when the Weatherlink
samples wind direction, it places a "marker" into one of sixteen "bins" which cor-
respond to the sixteen compass points. At the time of the archive, the Weatherlink
C
A L C U L A T I O N S
I S
NTERVAL AMPLE
every 5 seconds
every 5 seconds
every 5 seconds
every 8 seconds
every 15 seconds
every 30 seconds
every 60 seconds
R
ATE
T R
E C H N I C A L E F E R E N C E

Weather Data Calculations

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